Automatic choke



Oct. 4, 1955 A. H. wlNKLER i) 2,719,706

AUTOMATIC CHOKE Filed April a, 1952 /62 /lz [3l /50/1? a I I l 56' ATTOEMS'Y v United States Patent() AUTOMATIC CHOKE A Application April 8,1952, Serial No. 281,237 8 Claims. Y(Cl. zei- 39) The present inventionrelates to carburetors for internal combustion engines and moreparticularly to a choke control device for said carburetors.

One of the types of automatic choke devices widely used commercially onautomotive carburetors, consists of a thermostatic element responsive toengine temperature for closing the choke valve when the engine is coldand a piston responsive to manifold vacuum for moving the choke valve toa partially open position when the engine begins to tire. The extent towhich the choke valve is opened by the piston is determined by theposition of the vacuum conduit port in the sidewall of the cylinderhousing the piston. After being partially opened by the vacuum piston,the choke valve on moving to wide open position moves the piston in thecylinder over and beyond this vacuum port. As the piston passes over theport, there is a tendency for the manifold vacuum to restrict orcompletely prevent further movement of the piston. To overcome thisditiiculty, a longitudinal ilattened portion adjacent the vacuum porthas been provided on the piston to relieveV the effect of vacuum 'on thepiston side wall. This construction, however, causes a lowering in thedegree of effective vacuum available for actuating the piston throughthe' iirst portion of its stroke and thus tends to decrease the rate atwhich the piston will operate. It is` therefore one of the principalobjects of the present invention to provide a piston and cylinderconstruction for the aforesaid choke control device which permits theutilization ofl the full manifold vacuum transmitted to the cylinderwithout creating a condition which prevents the free movement of thepiston throughout its full stroke. K

Another object of the invention is to provide an automatic choke controldevice whichis readily responsive to engine operating conditions.

A further object of the invention is to provide a choke control devicein which the parts can be easily arranged to suit any particular type ofcarburetor or engine installation.

Additional objects and advantages -of the invention will become apparentfrom the following description and drawings wherein:

Figure l is a side elevation of a carburetor in which an automatic chokecontrol device .is shown in cross section;

Figure 2 is an enlarged, fragmentary cross-sectional view of the pistonand cylinder of the choke control device shown in Figure 1; and

Figure 3 is a fragmentary cross-sectional view of the piston andcylinder of a choke control device, showing a modified form of myinvention.

Referring more speciiically to the drawing, numeral designates the mainbody of a downdraft carburetor, 12 a throttle body, 14 a throttle valveand 16 an air horn in which is mounted a choke valve 18 on a shaft 20.The shaft is olset from the center of the induction passage to unbalancethe choke valve so that air ilow through the induction passage will tendto open the valve.

2,719,706 Patented Oct. 4,1'955 ICC The carburetor contains, in additionto those elements mentioned, a main fuel system, idle system,accelerating pump, fuel bowl and power enrichment jet, usually found inconventional float typeautomotive carburetors. A description of theseelements here is not necessary since their construction is well known.

` The choke valve 18 is controlled by an automatic choke unit mounted onthe air horn at one end of shaft 20 and consisting principally of ahousing 22, a thermostat 24 of a coiled bi-metallic material connectedto the choke shaft through a lever 26, and a vacuumactuated piston 28connected to lever 26 by a rod 30. 'I'he ythermostat is anchored at itscenter to a fixed pin 32 and is` hooked at its outer end over a pin 34on the free end of lever 26. As the engine cools, the thermostat uncoilsand urges the lever in a counterclockwise direction, i. e. in thedirection to close the choke valve. After the engine has started to rununder its own power and is becoming warm, the thermostat gradually coilsupon itself and backs the free end thereof away from pin 34, thuspermitting the choke valve to open under the inuence of air ilow in theinduction passage. Since the larger portion of the unbalanced valve ison the side moving downwardly as the valve opens, the valve tends tomove to and stay in open position and must be positively moved to andheld in closed or partly closed position. In the unit shown in thedrawing, the thermostat is capable of positively moving the choke valveonly toward closed position although in some installations it may bedesirable to secure the free end of the thermostat to pin 34 so that thechoke valve will be positively moved toward open position. j

The piston 28 is disposed in a cylinder 36 and consists of a hollowcylindrical member 40 having a land 42 at its inside end, another land44 at its outside end, and a central recess formed by ysaid lands andconnected by one or more ports 48 with the hollow interior of thepiston.

The cylinder which is closed at one end and connected directly at theother end with chamber 38 of the housing is connected at port 49 alongthe cylinder wall to the induction passage on the engine side of thethrottlevalve by conduit 50. The position of port 49 along the cylinderWall determines theextent to which the piston is moved by manifoldvacuum toward ,the right hand end of the cylinder after the enginebegins to fire yand thus determines the extent to which the choke valvewill be opened to provide the air required for cold engine operation.The port 49 is of larger diameter than the width of land 44 to preventthe land from sealing the port and being held by vacuum as it passesover the port. This arrangement eliminates the necessity of providingthe conventional slot in land 44 adjacent port 49 and therefore permitsthe utilization of the full vacuum transmitted to the cylinder. Whenkthe piston arrives at the position shown in Figure 1,A air `from chamber38 passing through the hollow interiorgof the piston through ports 48and around recess 46 to port 49 relieves the vacuum atthat port so thatit is ineffective to actuate the piston. The, piston can thereafter beeasily moved to its full right hand positionas the choke valve is movedtoward open position by air ilow in the induction passage.

-After land 44 passes port 49, manifold vacuum has no effect on themovement of the piston in either direction. The size of either port 49or land 44 may be varied in relation to the other in order to vary thevacuum in the closed end of the cylinder at the end of the vacuumactuated portion of the piston stroke to give a gradual transitionalmovement of the piston from the first part of the stroke to the lastpart. A restriction 54 may be included in conduit 50 so that the amountof vacuum transmitted to the cylinder may be varied from oneinstallation to another.

A modification of my invention is shown in Figure 3 wherein ableed 60and/or bleed zconnectconduit 50 with the Vclosed end of thecylinderVafter land 44 has passed Vover port `52 as it is moved by the chokevalve after .completion .of the vacuum stroke. This arrangement .permitsthe utilization .of a small amount of vacuum to assist in the movementVof the choke valve to `wide open position, and, by varying the relativesizes of port 48, lrestriction 54 and vbleeds 60 and/or 62, any desiredoperating characteristic may be obtained. Bleed y60 may be connected toconduit 50 either above or below Yrestriction S4. Other modications andarrange- .ments may be made without departing from the scope of theinvention.

'.1. .In a carburetor, an induction passage, a choke valve and athrottle valve in said passage, a shaft for said ychoke valve, a leversecured to said shaft, a cylinder, a piston in said cylinder connectedat one end to said vlever and having a land at the other end, and aconduit connecting said cylinder, along the side wall thereof at lapoint atleast partially traversed by said land, with said passage on theengine side of the throttle valve and having fat the point of juncturewith said cylinder a diameter greater than the width of said land.

f2. In a carburetor, an induction passage, a choke valve and a throttlevalve in said passage, a shaft for said choke valve, a lever secured tosaid shaft, a thermostatic means operatively connected to said lever, acylinder, a piston in .said cylinder connected at one end to said leverand having aland at the other end, and a conduit connecting saidcylinder, along the side wall thereof at a point at least partiallytraversed by said land, with said passage on the engine side of thethrottle valve and havling at the point of juncture with said cylinder adiameter greater `than the width of said land.

3. ln a carburetor, an induction passage, an unbalanced choke valve anda throttle in said passage, a shaft for said choke valve, a leversecured to said shaft, a thermostatic means operatively connected tosaid lever, a cylinder, a piston in said cylinder connected at one endto said lever and having an annular land at the other end, and a conduitconnectingv said cylinder, along the side wall thereof at a point atleast partially traversed by said land, with said passage on the engineside of the throttle and having at the point of juncture with saidcylinder a diameter greater than the width of said land, and arestriction in said conduit.

Y 4. In a carburetor, an induction passage, a choke valve and a throttlein said passage, a shaft for said choke valve, a lever secured to saidshaft, a coiled thermostatic means operatively .connected to said lever,a cylinder having a;closed end, a piston in said cylinder operativelyconnected to said choke valve and having an annular recess in theperiphery thereof forming an annular land on the end adjacent the closedend of said cylinder, and a conduit connecting said'cylinder, along theside wall thereof at a point at least .partially traversed by said land,with said passage on the engine side of the throttle and having at thepoint of juncture with said cylinder a diameter greater than the widthof said land.

5. In a carburetor, an induction passage, an unbalanced choke valve anda throttle in said passage, a shaft for said choke valve, a leversecured to said shaft, a coiled thermostatic means operatively connectedto said lever, a cylinder having a closed end, a piston in said cylinderoperatively connected to said lever and having an annular recess in theperiphery thereof forming an annular land on the end adjacent theclosedend of said cylinder, a conduit connecting said cylinder along theside wall vthereof with said passageon the engine side of the throttleand having at the point of juncture with said cylinder a diametergreater than the width of said land, and a bleed passage connectingsaidconduitwith said cylinder adjacent the closed end thereof.

6. A control device for a carburetor, comprising a thermostatic means, ahousing for said thermostatic means, a cylinder opening at one end intosaid housing and being closed at the other end, a pistonin said cylinderadapted to be connected to said choke valve and having a recess in theperiphery thereof, a land on the end of the piston adjacent the closedend of the cylinder, and a port in the .side wall of said cylinderat aypoint at least partially traversed by said land adapted -to be connectedwith a source of vacuum and having a diameter greater than the width ofsaid land. n

"7. A control device for a choke valve, comprising a thermostatic means,.a housing for said thermostatic means,a .cylinder opening at'one endinto said housing andibeing closed at the other end, a hollow piston-insaid cylinder adapted tobe operatively connected' to said choke valveandhaving an annular recess in the periphery thereof forming an annularland ,on the end of the piston adjacent the closed end of the cylinder,a passage` way in said piston adapted Vto connect said recess with saidhousing, and a port in the side Wall of said cylinder at a point atleastpartially traversed by said land adapted to be connected with a sourceof vacuum and having a diameter greater than the width of said land.

8. A control device for a choke valve comprising a thermostatic means, ahousing for said thermostatic means, al cylinder opening at one endintosaid housing and 'being closed at the other end, a hollow piston in saidcylinder adapted to be operatively connected to said choke valve andhaving an annular recess in the periphery'thereof lforming an annularland on the end of the piston adjacentV the closed end of thecylinder',` a passageway in said piston adapted toy connect said recesswith said `housing,.a port in the side wall of said cylinder adapted to`be connected with a source-of vacuum and having a diameter greater thanthe width of said land, and ableed .passage adapted 'to connect theclosed end of the cylinder with a source of vacuum when said land isbetween said port and said closed Vend References Cited in the tile ofthis patent j UNITED STATES PATENTS 2,031,709 Hunt Feb.'25, 19362,127,735 Hunt Aug. 23, 1938 2,215,682 Winkler Sept. "24, 19.402,499,607 Read Mar. '7, 1950 2,523,798 Winkler Sept. 26, 1950

